Combustible composition



1! S t s COMBUSTIBLE COMPOSITION No Drawing. Filed Apr. 6, 1959, Ser. No. 804,129

10 Claims. (Cl. 52-2) This invention relates to combustible compositions and more particularly to combustible compositions for use as ignition or delay charges in electric blasting caps.

Electric blasting cap charges comprise generally a base charge of a detonating explosive such as pentaerythritol tetranitrate, a heat-sensitive primer charge such as diazodinitrophenol superposed on the base charge, and a readily ignitable ignition charge capable of firing the primer charge by the heat generated. In the case of delay caps, an additional slow burning composition or delay fuse is generally included between the ignition and primer charges and exhibits such a predetermined rate of burning that a specified time interval elapses between the application of the firing current and the explosion of the primer charge. A constant objective sought in the manufacture of initiators and charges therefor is improved performance. This, of course, particularly applies to the compositons which are employed for the various charges.

Thus, the principal object of the present invention is to provide combustible compositions which possess improved ignitability and deflagrating characteristics, thereby rendering the compositions of special utility for use as ignition charges and delay charges, respectively.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

Generally described, the present invention comprises novel combustible compositions of lead oxide and metallic boride in which the compositions are advantageously applied as ignition charges in electric blasting caps and particularly in delay caps. Additionally, the compositions also may be used as delay fuses. More specifically, the compositions of this invention comprise lead oxide and metallic boride in the proportions of 95 to 40% and to 60% by weight, respectively.

An example of the improvement afforded by the invention is given for ignition compositions wherein red lead-manganese boride, a composition of this invention, is compared with other ignition compositions such as leadselenium and lead-tellurium. These compositions were prepared in intimate admixture and in condition for use in a blasting cap and then tested. The type of test employed and the data obtained are set forth in Table I following.

Unite I Table I Type of Test Pb O -MI1B2 Pb-Se Pb-Te Ignition temperature, 5 sec.

cm 25 8 25 Impact sensitivity, 10 lb.

wt -in 23 11 Heat of reaction, cal/g 162 86 61 Avg. burning time, 0.65 g.

charge -ms 209 60 160 From the foregoing data it is apparent that red leadmanganese boride has a number of advantages over both lead-selenium and lead-tellurium, the principal advantage being that it provides a hotter mixture and at the same time has a slower burning rate. Another advantage is its high ignition temperature which makes it more stable 'duri 2 ing high temperature. storage than either lead-selenium or lead-tellurium for certain critical uses.

Despite its high ignition temperature, red lead-manganese boride mixtures exhibit excellent series firing properties. This is illustrated in Table II below in which comparisons are made between red lead-manganese boride and lead-selenium and lead-telluriurn mixtures, both in straight series firing and in mixed series firing. In the former case the ignition compositions were evaluated as loose charges in electric blasting devices, in which 30 such caps were connected in a straight series. In the latter case, namely, mixed series firing, the same devices were evaluated in individual series comprising two regular E.B. caps plus ten delay EB. caps containing the ignition compositions mentioned above.

Table II Critical Firing Current (C.F.C.)

Ignition Mixture Straight Series, amp.

Mixed Series, amp.

95 99; QOJQQQ 99992- MWWWO PbT6, 61.9-38.1

Table III [High voltage, 220 v. A.C., 5, 10 and 20 caps in parallel] Ignition Mixture No. Tested Percent Failed 660 Pb-Se, 72.4-27.6

Although it is not intended that the invention shall be limited to any particular theory of operation, it appears that the improvement in performance of red lead-manganese boride over lead-selenium resides in the ability of the former mixture to produce more heat and as a consequence provide more positive ignition of the delay fuse.

This feature together with the substantially gasless char-.

acteristic of red lead-manganese boride composition imparts an outstanding combination of characteristics for utility in conjunction with delay initiating devices.

Still, a further advantage of red lead-manganese boride over Pb-Se is exemplified in Table IV wherein 10th period delay caps were used for obtaining the comparative storage data. Here is will be noted that the storage characteristics of the novel composition of this invention are superior to the lead-selenium composition.

Table IV F. Storage Period, months Slow-up in Av. Time After Storage, percent Ignition Mixture more" Other combinations of red lead and metallic borides have. shown satisfactory performance when evaluated as loose ignition charges in electric blasting caps, such as for example in series firing combination using 30 caps per series. This is illustrated in Table V. v

Table V one. 30' Delay in Ignition Mixture Series), amp.

Table VI Ignition Mixture No. Tested Results rho-A113,

Pb-ZfBz PbOrZr'B ,encnow-enow-enm Still another advantage of the invention will be appreciated from the data presented in Table VII. Here, it will be noted that the electrical properties of, lead oxidemetallic borides can be changed by altering the particle.

size of the fuel or the oxidizing agent. This is important for adjustment to obtain certain critical firing currents as required for certain end product uses. For example, when 200 mesh red lead-manganese boride (74 microns maximum) or finer is used, the results set forth in Table VII were obtained in mixed series firing tests.

Table V II Max. Particle Size 01' Boride, microns C.F.C. (2 Reg. E.B. Caps+10 Delays), amp.

Ignition Mixture PbgOrMllBg, 65-35--- Pb 0 Pbzor-Ml'lBg, 65-35.

With reference to the data which have been presented herein, it is evident that there are numerous factors which will influence conditions for the most satisfactory operation of the invention, the actual requirements of which are determined by the starting materials and the finished product desired.

' Generally, however, the order of preference of materials and their proportions are as follows: red lead-manganese boride from about 90/10 to about 60/40; red lead-aluminum boride from about 90/ 10 to about 50/50; and red lead-iron boride from about 88/12 to about 55/45, all proportions in percentage by weight as presented here and throughout the specification. Although the most preferred compositions are those containing red lead-manganese boride, other oxides of lead, such as PbO, PbO Pb O and Pb O, may be used and other borides such as aluminum, calcium, iron, tungsten and zirconium. Moreover, although the combustible corn;

positions of this invention have been described as having particular utility when used as ignition compositions or delay fuses or both for electric blasting caps, the beneficial burning characteristics of these new explosive com.- positions suggest their use in conjunction with heat actuated motors, gas generators and the like.

It will be seen, therefore, that this invention has many advantages and that the invention may be carried out by the use of various modifications and changes without departing from its spirit and scope, with only such limitations placed thereon as are imposed by the appended claims.

What I claim and desire to protect by Letters Patent is:

1. A combustible composition for utilization as a substantially gasless burning composition which comprises lead oxide and metallic boride of the group consisting of manganese boride, aluminum boride, calcium boride, iron boride, zirconium boride, and tungsten boride in the proportions of 95 to 40% and 5 to 60% by weight, respectively.

2. A combustible composition for utilization as a substantially gasless burning composition which comprises lead oxide and a metallic boride of the group consisting of manganese boride, aluminum boride, calcium boride, iron boride, zirconium boride, and tungsten boride in the proportions of about to 60% and about 10 to 40% by weight, respectively.

3. A combustible composition for utilization as a substantially gasless burning composition which comprises lead oxide and a metallic boride in the proportion of about 90 to 60% and about 10 to 40% by weight, respectively, and in which the metallic boride is manganese boride.

4. A combustible composition for utilization as a substantially gasless burning composition which comprises lead oxide and a metallic boride in the proportion of about 90 to 60% and about 10 to 40% by weight, respectively, and in which the metallic boride is aluminum boride.

5. A combustible composition for utilization as a substantially gasless burning composition which comprises lead oxide and a metallic boride in the proportion of about 90 to 60% and about 10 to 40% by weight, respectively, and in which the metallic boride is calcium boride.

6. A combustible composition for utilization as a substantially gasless burning composition which comprises lead oxide and a metallic boride in the proportion of about 90 to 60% and about 10 to 40% by weight, respectively, and in which the metallic boride is iron boride.

7. A combustible composition for utilization as a substantially gasless burning composition which comprises lead oxide and a metallic boride in the proportion of about 90 to 60% and about 10 to 40% by weight, respectively, and inwhich the metallic boride is zirconium boride.

8. A combustible composition for utilization as a substantially gasless burning composition which comprises red lead and manganese boride in the proportions of about 90 to 60% and about 10 to 40% by weight, respectively.

9. As combustible composition for utilization as a substantially gasless burning composition which comprises red lead and aluminum boride in the proportions of about 90 to 60% and about 10 to 40% by weight, respectively.

10. A combustible composition for utilization as a substantially gasless burning com-position which comprises red lead and iron boride in the proportions of about 90 to 60% and about 10 to 40% by weight, respectively.

References Cited in the file of this patent Moeller: Inorganic Chemistry, 1952, p. 773. (Copy in Sci. Lib.)

Stock; Hydrides of Boron and Silicon, 1957, pp. 4044. (Copy in Scientific Library. TP 245 B657.)

Schwarzkopf and Kieffer: Refractory Hard Metals, 1953, pp. 271-275. (Copy in Scientific Library. TN 677 536C.3.) 

1. A COMBUSTIBLE COMPOSITION FOR UTILIZATION AS A SUBSTANTIALLY GASLESS BURNING COMPOSITION WHICH COMPRISES LEAD OXIDE AND METALLIC BORIDE OF THE GROUP CONSISTING OF MANGANESE BORIDE, ALUMINUM BORIDE, CALCIUM BORIDE, IRON BORIDE, ZIRCONIUM BORIDE, AND TUNGSTEN BORIDE IN THE PROPORTIONS OF 95 TO 40% AND 5 TO 60% BY WEIGHT, RESPECTIVELY. 